1. Field of the Invention
The present invention relates to a frequency calibration method applicable in a Universal Serial Bus (USB) device and the related USB device, and more particularly, to a method of utilizing a polling low frequency periodic signal to calibrate an oscillator of a USB device and a related USB device thereof.
2. Description of the Prior Art
With the development in the technical field of the Universal Serial Bus (USB), the latest data transmission interface has been updated to USB 3.0. The maximum data transmission speed of the USB 3.0 reaches 5 Giga bits per second (Gbps). In other words, the operation clock of USB 3.0 device is at least 2.5 GHz. In a traditional design, a precise inductor capacitor oscillator (LC oscillator) is built in a USB 3.0 device, and the LC oscillator oscillates a reference clock having a precise frequency. Next, a signal synthesizer may be utilized to synthesize a 2.5 GHz operation clock. However, an LC oscillator usually occupies a very large chip area, resulting in an increased production cost of the USB 3.0 device. Hence, how to generate a reference clock having a precise frequency with a lower cost has become an important issue to be solved.